From one day to the other my printer's hotend won't reach its setpoint temperature anymore. The setpoint is set to 225, it heats up, but it is very, very slowly approaching only 215. And it seems like that with each subsequent attempt the maximum reachable temperature will be lower. I recycled the printer power and tried again, but this time it was only slowly creeping up to 207. The heatbed heats just fine. I don't think it is a problem with the power supply. I read on the SeeMeCNC forum that a PID re-tune might help, but I expect that the heating resistors might be at the end of their lifetime. Any other ideas?